The present invention relates to a system for sensing and automatically controlling the orientation of a work tool.
A variety of work machines can be equipped with tools for performing a work function. Examples of such machines include a wide variety of loaders, excavators, tele-handlers, and aerial lifts. A work vehicle such as backhoe loader may be equipped with a tool, such as a backhoe bucket or other structure, for excavating and material handling functions. A swing frame pivotally attaches to the frame of the vehicle, a boom pivotally attaches to the swing frame, a dipperstick pivotally attaches to the boom, and the tool pivotally attaches to the dipperstick about a bucket pivot. A vehicle operator controls the orientation of the tool relative to the dipperstick by a tool actuator. The operator also controls the rotational position of the boom relative to the vehicle frame, and the dipperstick relative to the boom, by corresponding actuators. The aforementioned actuators are typically comprised of one or more double acting hydraulic cylinders and a corresponding hydraulic circuit.
During a work operation with a backhoe bucket, such as lifting or excavating material, it is desirable to maintain an initial orientation relative to gravity to prevent premature dumping of material, or to obtain a constant excavation shear angle. To maintain the initial backhoe bucket orientation relative to gravity, the operator is required to continually manipulate the backhoe bucket command input device to adjust the backhoe bucket orientation as the backhoe boom and dipperstick are moved during the work operation. The continual adjustment of the backhoe bucket orientation, combined with the simultaneous manipulation of a backhoe boom command input device and a dipperstick command input device inherent in movement of the backhoe boom and dipperstick, requires a degree of operator attention and manual effort that diminishes overall work efficiency and increases operator fatigue.
A number of mechanism and systems have been used to automatically control the orientation of a tool such as a backhoe bucket. Various examples of electronic sensing and control systems are disclosed in U.S. Pat. Nos. 4,923,326, 4,844,685, 5,356,260, and 6,233,511. Control systems typical of the prior art utilize position sensors attached at various locations on the work vehicle to sense and control tool orientation relative to the vehicle frame. Unlike the typical prior art, the present invention makes use of an angular velocity sensor attached to the tool to sense and maintain a fixed work tool orientation relative to an initial orientation, independent of vehicle frame orientation. The result is a simpler control system and improved tool orientation control relative to gravity.
A number of angular velocity sensors suitable for use in the present invention are commercially available. Examples of these types of angular velocity sensor are disclosed in U.S. Pat. Nos. 4,628,734, 5,850,035, 6,003,373. One example of such an angular velocity sensors is the BEI GYROCHIP(copyright) Model AQRS, marketed by the Systron Donner Internal Division of BEI Technologies of California.
The object of the present invention is to provide for an improved system for sensing and automatically controlling the orientation of a tool pivotally attached to a dipperstick of a backhoe or excavator.
The system automatically controls work tool orientation by making use of an angular velocity sensor attached to the tool to sense angular velocity of the tool relative to a global earth reference. A controller maintains the tool at a selected angular velocity.
The illustrated invention comprises a backhoe, a swing frame pivotally attached to the frame of the backhoe, a boom pivotally attached to the swing frame, a dipperstick pivotally attached to the boom, a tool pivotally attached to the dipperstick, an actuator for controllably moving the tool about its pivot, and the aforementioned angular velocity sensor. A controller processes data from the angular velocity sensor and commands movement of the tool actuator in response thereto. The illustrated embodiment also includes a tool command input device to affect movement of tool actuator, and a tool auto-hold command input device to enable a tool auto-hold function for maintaining the tool in an initial orientation.
When the tool auto-hold function is enabled, the controller maintains the tool orientation by commanding the tool actuator to move the tool such that the angular velocity sensed is zero. The controller is adapted to discontinue the tool auto-hold function when the operator manipulates the tool command input device to affect tool movement. The controller resumes tool auto-hold function once the operator discontinues manipulation of the tool command input device, reestablishing the initial tool orientation at the new orientation affected by the operator. Additionally, the operator may manipulate an auto-hold command input device to selectively enable and disable the tool auto-hold function.